Dude,
If you can find and keep an Octopus cyanea you will be in for a serious treat! O. cyanea is a fairly large diurnal octopus, sporting a mantle length about the size of a coconut but it is capable of some really wild color changes and even wilder texture changes! They are nearly impossible to get in this country, but through my research connections I managed to acquire one a few years ago. An AMAZING animal.
It didn't last long, unfortunately. My tank went through an 8 month period where it killed cephalopods relentlessly and the cyanea was it's first victim.
Rock on, Jimbo